N-cadherin is required for the differentiation and initial myofibrillogenesis of chick cardiomyocytes.
To investigate initial stages of cardiac myofibrillogenesis, heart-forming mesoderm was excised from stage 6 chick embryos and explanted on fibronectin-coated coverglasses. The explants were fixed at various times and immunofluorescently stained with antibodies to N-cadherin, alpha-catenin, beta-catenin, sarcomeric myosin, pan and sarcomeric alpha-actinins, or rhodamine phalloidin. After 7 hours in culture the cells appeared epithelial. N-cadherin, alpha- and beta-catenin, pan alpha-actinin, and F-actin showed circumferential localization at cell borders. No cells in the explant were positive for sarcomeric alpha-actinin or sarcomeric myosin at this stage. Sarcomeric alpha-actinin and sarcomeric myosin were detected around 10 hours after plating. Sarcomeric alpha-actinin initially appeared as small beads along thin actin filaments. Mature Z-lines began to be organized at 20 hours, at the same time the cells started to contract. When the rat monoclonal antibody NCD-2, which inhibits N-cadherin function, was added to the culture at early time-points, cells lost cell-cell contacts, became spherical in shape, and contained tangled actin fibers. The expression of sarcomeric alpha-actinin and sarcomeric myosin was suppressed. These results indicate that 1) the precardiac mesoderm explant cells differentiate and form well-organized myofibrils in culture, 2) N-cadherin-mediated cell-cell interactions are necessary for early differentiation of cardiomyocytes and organization of myofibrils.
Imanaka-Yoshida
K
K
Department of Pathology, Mie University, School of Medicine, Tsu, Japan. imanaka@doc.medic.mie-u.ac.jp
Knudsen
K A
KA
Linask
K K
KK
D000818:Animals; D015820:Cadherins / Q000502:physiology*; D002454:Cell Differentiation / Q000187:drug effects; D002642:Chick Embryo; D046508:Culture Techniques; D008648:Mesoderm / Q000166:cytology / Q000502:physiology; D009206:Myocardium / Q000166:cytology*; D009210:Myofibrils / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology*; D051381:Rats
D015820:Cadherins